While draining liquid from a tank or other similar enclosure, formation of a coriolis effect vortex or a vortex induced by the approach flow geometry is commonly encountered. The likelihood of such a vortex formation increases as the ratio of the height of the liquid above the drain compared to the diameter of the drain decreases. In other words, decreasing liquid levels and/or increasing drain sizes increase the likelihood of vortex formation. Another factor which can increase the likelihood of vortex formation is increasing drain flow rates, such as where a suction pump is connected to the drain to pull liquid from the enclosure.
Typical nuclear and chemical plants have numerous tanks which are commonly drained to levels in which the free surface between a gas and liquid can approach the drain level (discharge). Commonly, the discharge from such tanks is connected to suction pumps which expedite removal of the liquid from the tank. Experiments have shown that, under certain conditions, a vortex could be formed that permits gas from the freeboard space above the surface of the liquid to be pulled into the suction flow. Such a vortex is undesirable because it can limit the rate at which the liquid can be drained from the tank and can lead to cavitation in the suction (drain) pump. Accumulation of gas in a pump can result in a significant decrease in the pumping capacity and potentially damage the pump internals.
For tanks which have been designed to drain the liquid level to elevations that approach a depth where such a vortex could be formed, it is desirable to provide a device that prevents the formation of a sufficiently strong vortex capable of pulling a continuous gas core into the suction piping and pump.
It is also desirable to provide a device capable of being retrofit to existing tank outlets and suction piping inlets which may have limited accessibility.
It is also desirable that such a device be of reliable construction in both material and design for use in applications where harsh conditions and limited access provide for limited inspection and maintenance.